Ventilating system

ABSTRACT

A system is provided for selectively controlling the movement of air through a passageway by means of a damper operated by an actuator which, in turn, is controlled by a movable selector. In a specific embodiment, the movable selector determines a preset position of the damper, which is caused to move from the preset position to a back draft position when the system is shut down. When the system is again energized, the damper is automatically returned to the position determined by the movable selector.

United States Patent LOW VOLTAGE POWER 2 c, SUPP] PUMP 1,895,880 l/1933 Cummings 251/131 X 2,150,117 3/1939 Griffith 251/131 X 3,307,824 3/1967 Weisheit 251/131 2,836,191 5/1958 Wallin et al 251/212 FOREIGN PATENTS 82,841 3/1935 Sweden 251/131 Primary Examiner-Arnold Rosenthal Attorney-Anderson, Luedeka, Fitch, Even and Tabin ABSTRACT: A system is provided for selectively controlling the movement of air through a passageway by means of a damper operated by an actuator which, in turn, is controlled by a movable selector. In a specific embodiment, the movable selector determines a preset position of the damper. which is caused tomove from the preset position to a back draft position when the system is shut down. When the system is again energized, the damper is automatically returned to the position determined by the movable selector.

OSlTlVE POSITIONl MG CIRCUIT PATENTED OCT 5 I971 CONTROL LA INVENTOR ROBERT M. STUCK ATTYS.

VENTILA'IING SYSTEM The present invention relates to damper-controlled ventilation systems and, more particularly, to such system in which the position of the damper is selectively adjustable to permit control of the airflow within the system.

One form of ventilation system commonly employed in buildings, particularly large buildings, includes a roof ventilator containing an exhaust or input fan which is in communication with a main airflow duct located within the building. Conventionally, the main airflow duct communicates with feeder ducts which lead to various rooms, thereby providing ventilation throughout the building.

In order to provide some control over the volume of air being circulated, a damper is provided in one or more of the ducts which partially or fully obstructs the flow of air. A frequently used damper includes vanes which extend transversely of the duct and which are mounted for uniform pivotal movement to various positions. Selective positioning of the damper vanes is accomplished by a mover mechanically coupled to the vanes, and a selector is normally positioned within a room of the building to control the operation of the mover.

In a system frequently employed, the mover includes a reversible electric motor which is constantly energized and coupled to the vanes by some form of clutch mechanism electrically connected to the selector. An alternate system may include a so-called SELSYN motor-generator combination, one of which is connected to the selector and the other of which is connected to the damper. In either case, when the selector is moved to a predetermined setting, the damper vanes are moved to a corresponding position and maintained in that position until the selector is again moved. The most desirable setting of the selector is invariably determined by trial and error for each particular damper in a given environment.

One principal disadvantage to such systems is that it is frequently desirable to place the damper vanes in a so-called back draft position when the roof ventilator fan is not operating, as when the building is not in use. For example, where an exhaust-type roof ventilator is employed, it is desirable to prevent a backflow of outside air into the building during cold weather. With the conventional motor-operated damper, however, a back draft position of the damper can be achieved only by moving the selector to a closed setting. When the roof ventilator fan is again energized, it becomes necessary to also reset the selector for each damper in the building to again return the damper vanes to the desired position. If the most desirable conditions are again to be achieved, it is also necessary for the person resetting the selector to be aware of and recall the previously determined setting.

An alternative to the continued resetting of the selectively positionable dampers is to provide an additional damper which functions only to prevent back draft. The provision of such an additional damper, which may include vanes biased to a closed position and automatically opened by the force of the airflow, adds an additional cost factor to the system, and creates additional resistance to airflow. Accordingly, this alternative is also not completely satisfactory.

It is the principal object of the present invention to provide an improved air ventilation system.

A further object of the present invention is to provide a damper control for an air ventilation system in which the damper can be caused to assume a back draft position, as when the system is shut down, but can be caused to return to a desired predetermined position automatically, as when the system is again activated.

These and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings of which:

FIG. 1 is a diagrammatic representation of an air ventilation system showing various features of the invention;

FIG. 2 is a perspective view of one embodiment of a damper unit which can be included in the system of FIG. 1;

FIG. 3 is a side elevational view of the damper unit of FIG. 2; and

FIG. 4 is a schematic view of a portion of the electrical circuit of the system of FIG. 1.

Briefly, there is illustrated in FIG. I a preferred embodiment of an air ventilation system incorporating various of the features of the invention. The system as shown includes a damper 10 having vanes 12 mounted in a passageway 13 in such a manner as to permit pivotal movement of the vanes about fixed axes between an open and a closed position relative to the passageway. As best seen in FIG. 2, the vanes 12 are preferably interconnected so that they all move in unison and, as illustrated, are biased, as by a spring 14, toward a passageway-obstructing or closed position.

The vanes are mechanically linked, as by a rod 15, to a mover in the form of an actuator 16 which provides the necessary force to overcome the biasing force of the spring 14 and to move the vanes to any desired position. In the illustrated embodiment, the actuator 16 is electrically connected to a power supply 18 through a switch 20, which also controls the flow of current to a fan 21, and through a positive positioning circuit 22 including a selector in the fonn of a potentiometer 24 which, in the illustrated embodiment, is manually adjustable and preferably located in a room of the building being ventilated. However, the potentiometer 24 could be replaced by a device capable of changing resistance in response to parameters such as temperature, pressure, etc. The positioning circuit 22 is in turn electrically connected to a second potentiometer 26 which is mechanically linked to the damper unit 10.

The potentiometers tend to assume identical or balancing positions when current is flowing through the circuit. Accordingly, when the circuit is opened to halt the operation of the fan, the damper vanes assume a closed or back draft position due to the biasing force of the spring 14 on the damper and the lack of any opposing force by the actuator, which has also been deenergized. This movement of the vanes to the back draft position also moves the potentiometer 26 out of a balancing position with the potentiometer 24 due to the mechanical linkage between the potentiometer 26 and the damper vanes. When the circuit is again closed to energize the fan, the actuator is also energized and begins to exert a force on the damper vanes in opposition to the biasing force of the spring, thereby moving the damper vanes toward an open position. When the vanes reach a position in which the potentiometer 26 is in balance with the potentiometer 24, which has remained in its preset position, the actuator will cease to move the vanes and will maintain them in such' position unless the. setting of the potentiometer 24 is changed or until the system is again deenergized.

Thus, in the operation of the system, the damper assumes the desired back draft position when the fan is shut off but automatically returns to a desired preset position when the fan is again turned on without the necessity of resetting a manual selector located remote from the damper.

More specifically, the damper 10, shown most clearly in FIGS. 1 through 3, includes rectangular metal frame 28 having a plate or flange 27 projecting from one of its lower side edges to support the actuator 16 and. various other elements, as hereinafter described. In the illustrated embodiment, seven of the vanes 12 are pivotally mounted on the frame so as to extend between the sidewalls in generally parallel relation to one another. It is understood, of course, that the damper might also constitute a single plate pivotally mounted, or even slidably mounted for insertion into and out of the passageway 13 somewhat in the manner of a gate valve.

Each vane 12 may comprise simply a flat strip of metal provided with a pair of spaced longitudinally extending parallel reinforcing ribs 29, or may be an extruded or fabricated hollow member of airfoil contour. Each vane is of such a length and width that when the vanes all lie in a single plane edge to edge and in parallel relation to each other, they occupy essentially the entire opening defined by the frame so as to completely obstruct the opening, thereby serving a back draft function. A centrally located stub shaft 30 is provided at each end of each vane and serves as the means by which it is pivotally mounted. The shafts 30 project through and are journaled in openings in the sidewall of the frame 28.

The vanes are caused to move in unison by a gear train, best seen in FIGS 2 and 3, which comprises identical spur gears 32, one of which is keyed to that end of the shaft 30 of each vane which projects through one of the sidewalls of the frame. In the illustrated embodiment, the gears mesh with each other so that each gear rotates in a direction opposite to that of the adjacent gear (FIG. 3). If desired, however, a rack and pinion arrangement could be employed so that the gears would all rotate in the same direction. Alternatively, mechanical linkages other than gears may be employed to effect the desired movement of the vanes, or any other suitable linkage which causes all of the vanes 12 to move simultaneously to a fixed position would be satisfactory.

The vanes are theoretically rotatable through an angle of 360'. However, as a practical matter, it is necessary only that they rotate 90 from a back draft position to a position in which they lie in planes parallel to the flow of air through the passageway and thus provide the least obstruction to the flow of air. Movement of the vanes between such positions may be limited in various ways. For example, the actuator 16 and the linkage connecting it to the vanes may be designed so as to permit movement of the linkage only within fixed limits. Electrical stops such as microswitches could also be suitably located to deenergize the actuator when the vanes reach predetermined positions. Still further, fixed stops could be provided on the damper frame to engage the vanes and prevent movement past predetermined positions. An illustration of the latter form of construction is provided in the drawings and includes a flange 33 which overhangs an edge portion of the vane located nearest one end of the frame (the left end in FIG. 2) to prevent rotation of that vane and, hence, all of the vanes geared thereto, past the back draft position when the vanes are rotating toward such position. Similarly, a bracket 34 is affixed to the inner surface of each of the sidewalls of the frame to engage a centrally located vane and prevent more than a 90 movement of that and the other vanes away from the back draft position. Of course, if desired, one or more brackets could be substituted for the flange 33 and bracket 34 to achieve other limits of the rotation of the vanes. As shown, however, the vanes are capable of an infinite number of positions between the back draft or closed position and the fully open position 90 of rotation therefrom.

The vanes 12 areconnected to the actuator 16 by a linkage which includes the rod 15. More specifically, the actuator 16 is mounted on the support plate 27 by means of a bracket 36 which includes an upstanding plate 38. Extending from the lower end of the plate in perpendicular relation thereto is an arm 40, to the outer end of which is pivotally secured the lower end of a link 42. The link 42 has a pivot pin 44 extending laterally outwardly therefrom approximately midway of its height for rotation about an axis parallel to the axes of rotation of the vanes 12. The pivot pin is provided with a hole transverse to its axis of rotation which receives one end of the rod 15. The opposite end of the rod is pinned for rotation to the face of one of the spur gears 32. As an alternate construction, the opposite end of the rod might be pinned to a lever projecting radially from one of the shafts 30.

Thus, when the link 42 is pivoted about its lower end, the rod is moved generally longitudinally to efiect rotation of the vanes 12. The spring 14 is connected between the upper end of the link and the housing of the actuator 16 so as to bias the upper end of the link toward the actuator to a position in which the damper is closed.

It should be apparent, of course, that various other linkages can be devised for connecting the actuator 16 and vanes 12 and that the linkage shown is only one of various linkages conceivable. Also, the spring 14 could be connected to other portions of the linkage, or could even be contained within the actuator housing.

The movement of the vanes 12 is caused by the actuator 16 which, in the illustrated embodiment, includes a housing 46 defining an hydraulic cylinder 48 (FIG. 1) within which is carried a piston 50. A rod 52 is connected to the piston and projects outwardly of the housing and is pinned to the link 42. When the piston rod is extended in response to an hydraulic pressure within the actuator cylinder, the link 42 is pivoted and causes the damper vanes to be rotated away from the back draft position. When the pressure within the hydraulic cylinder is relieved, the spring 14 causes the piston rod 48 to be retracted.

Hydraulic pressure is created within the hydraulic cylinder 48 by means of an hydraulic pump 54 driven by an electric motor 56. The pump is in fluid communication with the hydraulic cylinder 48 through a suitable passageway or conduit having an inlet 58 into the cylinder and by a conduit or passageway having an outlet 60 out of the cylinder. An electrically operated valve 62 is provided adjacent the outlet 60 and is capable of controlling the amount of fluid flowing out of the cylinder.

In this regard, the outlet valve 62 includes means (not shown) which are capable of limiting the flow of fluid through the outlet such as, for example, means for restricting an orifice through which the fluid flows. The limiting or restricting means are preferably biased toward a position which permits the fluid entering the cylinder 48 to pass through the cylinder without causing a pressure sufficient to move the piston 50. It is contemplated that the output of the pump will remain constant so that restriction of the outlet by the valve creates an hydraulic pressure on the piston 50.

Electrical power for the system is provided by the power source 18 which, as shown, supplies 220 volt AC three-phase current. The flow of current through all three lines leading from the power source is controlled by the switch 20 so that when the switch is open, no current is supplied to any of the components of the system. Suitable lines are tapped off the main lines to provide power to the fan 21 which, in a preferred embodiment, is powered by a three-phase 220-volt motor.

Two of the lines in addition supply single-phase 220-volt power to the pump motor, which includes a stepdown transformer, and to a low-voltage power supply 64 which includes a rectifier to provide low-voltage DC current to the positive positioning circuit 22 and the valve 62.

The positive positioning circuit 22 assures that the damper vanes will return to the desired position after the switch 20 has been opened and the air ventilation system is again activated. It may be located within the housing 46 of the actuator 16 or elsewhere in the building such as, for example, at the location of the manually adjustable potentiometer 24. One embodiment of a positive positioning circuit is illustrated in FIG. 4. The active power input to the control circuit is received from the DC power supply 64 through leads labeled R and B. The circuit itself is made-up of a control portion 66 including the manually adjustable potentiometer 24 and the potentiometer 26 physically connected to the vanes 12. The circuit also includes a regulator portion 68 which transmits a signal from the control portion 66 back to the outlet valve 62, causing the valve to open or close in response to the signal. The manually adjustable potentiometer 24 and the potentiometer 26 are connected in parallel (Fig. 4) and act as a bridge, with the potentiometer 26 providing feedback. In operation, initial closing of the switch 20 will provide sufficient current to the valve 62 to close the valve against the force biasing it to the open position, thereby allowing pressure to build up within the actuator cylinder 48, causing the piston 50 to move and, in doing so, to move the vanes away from the back draft position. When the movement of the vanes is sufficient to cause the potentiometer 26 to reach a position balancing the position of the manually adjustable potentiometer 24, the output current flow to the outlet valve 62 is reduced to provide a signal for achieving equilibrium between the hydraulic force on the piston 50 and the force of the spring 14 which urges the vanes toward the back draft position. This balancing position of the potentiometers corresponds to the setting of the manual potentiometer 24. As long as the current to the valve 62 remains constant, the system is stabilized with the vanes 12 at the desired position.

Should the manually adjustable potentiometer 24 be adjusted to a different setting, the equilibrium of the system is temporarily upset and a new equilibrium is established at the new setting, with the position of the vanes being correspondingly altered. Likewise, if the vane position is disturbed by some external influence the output current to the valve 62 will be altered to produce a restoring force on the piston 50 to maintain or restore the preset or desired vane position.

The output voltage of the low voltage power supply, having the polarity as indicated in FIG. 1, is supplied to the control portion 66 and regulator portion 68 of the positive positioning circuit 22 (FIG. 4) through supply leads 70 and 72, which are the leads R and B, respectively, of FIG. 1, the former being positive with respect to the latter. A filter capacitor 74 is connected across these leads. The control portion of the circuit includes a PNP control transistor 76 having its emitter coupled to the positive supply lead 70 through a biasing resistor 78 and its collector coupled to the relatively negative supply lead 72 through a collector resistor 80 and a load resistor 82. The base of control transistor 76 is coupled to the bridge formed by the potentiometer 26 and the manually adjustable potentiometer 24, the potentiometer 26 being connected in parallel with the series connection of resistor 84 and the manually adjustable potentiometer. The tap or wiper terminals of each potentiometer are electrically connected together and electrically coupled to the base of the control transistor 76. The bias circuit of control transistor 76 is completed by a biasing resistor 86 connecting the low potential side of the bridge to the negative supply lead 72. The control portion of the circuit controls the regulating portion by the potential developed across the load resistor 82 which is coupled to the base of the regulator transistor 88 through a diode 90 poled as shown in FIG. 4. The emitter of the regulator transistor 88 is connected directly to the positive supply lead 70 and its collector is connected directly to the output lead Y of the positive positioning circuit 22. A protective capacitor 92 is coupled across the emitter and collector of the regulator transistor 88.

in operation, when the supply voltage is initially applied to supply leads 70 and 72 upon closure of the line switch 20, the vanes are in their closed position and the potentiometer 26 is at a value creating an unbalanced bridge condition. With this bridge condition, the control transistor 76 is maintained in a nonconductive state by the application of a sufficiently high positive potential to its base. Thus, no significant voltage drop is developed across the load resistor 82 and the potential on the cathode of the diode 90 is substantially the same as the negative supply lead 72, causing the emitter-base junction of the regulator transistor 88 to be forward biased, placing this transistor in its conductive state. Current thus flows from positive supply lead 70, through regulator transistor 88, and through the valve 62 causing some given amount of flow restriction. As the actuator 16 causes the vanes 12 to move toward their fully open position, the resistance of the potentiometer 26 moves in a direction which will cause bridge balance and eventually produce a sufficiently low positive potential on the base of control transistor 76 to forward bias the emitter-base junction thereof, producing a conductive transistor condition. Current then flows through the emitter- .collector circuit of this transistor and through load resistor 82,

producing an increased positive potential on the cathode of the diode 90. This positive potential decreases the regulator transistor collector current on output lead Y, and may reduce this current to zero if a sufficiently high positive potential is developed across the load resistor 82 to reverse bias the diode 90. In either case, the component values are selected so as to produce sufficient opening of the valve 62 so that a condition is reached wherein the hydraulic forces on the piston are in equilibrium with the counter-acting force of the spring 14 and the pressure, if any, of the air on the vanes, to maintain the vanes at a predetermined position corresponding to the particular setting of the manually adjustable potentiometer 24. Any external force on the vanes that results in a rotation of the shaft of the potentiometer 26 will change the potential on the control transistor base, causing the regulator transistor 88 to alter the valve opening in the direction which results in a restoring action of the actuator piston, and consequently of the vane position, until equilibrium has been reached. Altering the manually adjustable potentiometer 24 to a new setting will likewise change the potential of the base of the control transistor 76, causing the regulating transistor to alter the valve aperture to establish a new system equilibrium at the new vane position. The system thus insures a positive positioning of the vanes regardless of variations in air pressure, hysteresis effects in the biasing spring, etc.

When the line switch is opened, the supply voltage on the positive positioning circuit is removed and the output signal on the lead Y returns to its no-current condition. However, when the line switch is again closed, the actuator will cause the vanes 12 to be opened to their previous position as determined by the setting of the manually adjustable potentiometer 24.

The positive positioning circuit 22 has only been generally described since the embodiment illustrated is shown merely by way of example of the type of circuit which might be employed.

The potentiometers employed in the illustrated embodiment are rotative potentiometers. The manually adjustable or first potentiometer 24 is set by rotating a dial 94 to the desired setting. The second potentiometer 26 is shown mounted on the frame of the damper 10 so as to be responsive to rotation of a shaft 30 of one of the vanes 12. While the potentiometers shown are rotative, linear potentiometers could be substituted for either or both potentiometers. If the linear-type potentiometer is employed as a monitor it may be affixed to any suitable base connected to any portion of the mechanism which directly monitors the movement of the vanes as, for example, the rod 15.

While in the illustrated embodiment, movement of the vanes is effected and controlled by a motor-pump actuator and a positioning circuit which includes balancing potentiometers, similar results could be accomplished by modifying the system described or by other significantly different systems. For example, the circuit could be designed so that when the fan ceased to operate, the valve 62 became fully opened but the pump motor and pump continued to operate. The biasing spring 14 would in such case still return the vanes to the back draft position. Also, it is possible that the fan be omitted in a natural draft system.

The system of the illustrated embodiment and those modifications described by way of example permit a damper to be accurately set for any desired amount of airflow. The system may be shut down at the end of a day and reactivated later without the necessity of readjustment. The damper automatically closes when the system is shut down to become a back draft damper. Besides automatically returning to a set position upon reactivation, the control permits very accurate adjustment of the airflow during operation should a change be desired.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. A system for selectively controlling the movement of air through a passageway, said system comprising a damper movably mounted so as to enable it to occupy a first position and a plurality of secondary positions, an actuator mechanically connected to said damper capable of moving said damper to and maintaining it in a predetermined secondary position, a movable selector connected to said actuator for designating a predetermined secondary position when placed in a predetermined setting, means for causing said actuator to move said damper to and maintain it in the designated predetermined secondary position, means for causing said actuator to cease to maintain said damper in said predetermined secondary position and for causing said damper to be returned to said first position without disturbing the selector setting, and means for causing said actuator to return said damper from said first position to said predetermined secondary position designated by the setting of said selector without readjustment of said selector, said means for causing said actuator to return said damper from said first position to said predetermined secondary position comprising a first potentiometer operatively connected to said selector and responsive to the setting thereof and a second potentiometer linked to said damper and responsive to the position thereof, said second potentiometer being connected to said actuator and capable of controlling the operation thereof so that return of said damper to said predetermined secondary position is achieved when said potentiometers are balanced, said actuator comprising a piston carried within an hydraulic cylinder, said piston being mechanically linked to said damper to transmit movement of said piston to said damper, a motor operated pump capable of creating an hydraulic pressure, means connecting said pump to said hydraulic cylinder through an electrically operated valve capable of regulating the pressure applied to said piston, and said second potentiometer being connected to and controlling the operation of said valve. 

1. A system for selectively controlling the movement of air through a passageway, said system comprising a damper movably mounted so as to enable it to occupy a first position and a plurality of secondary positions, an actuator mechanically connected to said damper capable of moving said damper to and maintaining it in a predetermined secondary position, a movable selector connected to said actuator for designating a predetermined secondary position when placed in a predetermined setting, means for causing said actuator to move said damper to and maintain it in the designated predetermined secondary position, means for causing said actuator to cease to maintain said damper in said predetermined secondary position and for causing said damper to be returned to said first position without disturbing the selector setting, and means for causing said actuator to return said damper from said first position to said predetermined secondary position designated by the setting of said selector without readjustment of said selector, said means for causing said actuator to return said damper from said first position to said predetermined secondary position comprising a first potentiometer operatively connected to said selector and responsive to the setting thereof and a second potentiometer linked to said damper and responsive to the position thereof, said second potentiometer being connected to said actuator and capable of controlling the operation thereof so that return of said damper to said predetermined secondary position is achieved when said potentiometers are balanced, said actuator comprising a piston carried within an hydraulic cylinder, said piston being mechanically linked to said damper to transmit movement of said piston to said damper, a motor operated pump capable of creating an hydraulic pressure, means connecting said pump to said hydraulic cylinder through an electrically operated valve capablE of regulating the pressure applied to said piston, and said second potentiometer being connected to and controlling the operation of said valve. 